Another way to solve this is to use the Midpoint Formula. The midpoint of a segment joining points

and

is

So the midpoint of your segment is

Perhaps it helps to see that the x-coordinate of the midpoint is just the average of the x-coordinates of the points. Ditto for the y-coordinate of the midpoint; just average the y's.
Answer:
1
Step-by-step explanation:
the y-intercept is -1 since 4-3 is 1
Basically each part of the first complex number gets multiplied by each part of the second complex number. You are multiplying 2 binomials.
(15 + 56i(7 + 4i)
= 105 + 60i + 392i + 224i^2
= 105 + 452i - 224 ( because i^2 = -1)
= - 119 + 452i